Abstract:The overproduction of hydrogen peroxide is implicated in the progress of numerous life-threatening diseases and there is a great need for the development of contrast agents that can detect hydrogen peroxide in vivo. In this communication, we present a new contrast agent for hydrogen peroxide, termed peroxalate micelles, which detect hydrogen peroxide through chemiluminescence, and have the physical/chemical properties needed for in vivo imaging applications. The peroxalate micelles are composed of amphiphilic peroxalate based copolymers and the fl uorescent dye rubrene, they have a 'stealth' polyethylene glycol (PEG) corona to evade macrophage phagocytosis, and a diameter of 33 nm to enhance extravasation into permeable tissues. The peroxalate micelles can detect nanomolar concentrations of hydrogen peroxide (Ͼ50 nM) and thus have the sensitivity needed to detect physiological concentrations of hydrogen peroxide. We anticipate numerous applications of the peroxalate micelles for in vivo imaging of hydrogen peroxide, given their high sensitivity, small size, and biocompatible PEG corona.

Hydrogen peroxide is one of the fundamental molecules of biology, regulating key cell signaling pathways and the development of numerous inflammatory diseases. There is therefore great interest in developing contrast agents that can detect hydrogen peroxide in vitro and in vivo. In this report, we present a new contrast agent for imaging hydrogen peroxide, termed the chemiluminescent poly(ethylene glycol)-b-poly(e-caprolactone) (PEGPCL) micelles (CPMs), which can detect hydrogen peroxide at nanomolar concentrations and chemiluminesce in the near IR range (676 nm) in the presence of hydrogen peroxide. The CPMs are composed of a PEG-PCL scaffold and have fluorescent dyes and peroxalate esters in their hydrophobic PCL core. The CPMs image hydrogen peroxide by undergoing a three-component chemiluminescent reaction involving a peroxalate ester, a fluorescent dye, and hydrogen peroxide. The CPMs also have a stealth PEG corona to enhance their circulation half life. The CPMs should find numerous applications for imaging hydrogen peroxide because of their nanomolar sensitivity, small size, and stealth pegylated surface.

Epothilones, dolastatins (auristatins), tubulysins, duocarmycins, and enediynes are among the most potent anticancer agents, which inhibit cell growth of cancer cells with a low or subnanomolar activity. Epothilones inhibit tumor growth by stabilizing the microtubules in a manner similar to Taxol. There are hundreds of natural and synthetic epothilones known, and some of them are undergoing clinical trials. One semisynthetic analog, ixabepilone, has also been approved for the treatment of metastatic breat cancer. Similarly, there are numerous dolastatins, their synthetic analogs - auristatins, and tubulysins known, of which auristatins are currently being developed by Seattle Genetics, Inc. These compounds also inhibit microtubules, however unlike epothilones and Taxol, they function by destabilizing the microtubules. The other compounds, duocarmycins and enediynes, cause toxicity by interacting with DNA; duocarmycins alkylate DNA whereas enediynes cleave. At least one enediyne antibody conjugate, Mylotarg (or Gemtuzumab ozogamycin), prepared from calicheamicin and targeted to CD33, is an approved therapy for the treatment of acute myeloid leukemia. Not surprisingly, most of these naturally occurring compounds or their synthetic analogs also cause nonselective toxicities to the rapidly dividing normal cells, including those from hair follicles, bone marrow, and gastrointestinal lining. To minimize such indiscriminate toxicity, these compounds can be conjugated to tumor-targeting antibodies, as the case is with auristatins and calicheamicin. While we are developing antibody conjugates, we have also been focusing on a prodrug approach, in that the prodrugs can be activated selectively in tumor and tumor microenvironments by the endogenous tumor-associated proteases. Alternatively, an exogenous enzyme, such as aldolase antibody, 38C2, that are directed using low molecular weight inhibitors of the cell surface receptors overexpressed in tumor cells and tumor microenvironments, can also catalyze the prodrug activation. In this presentation, we will be discussing our studies toward the synthesis and evaluation of many of these cytotoxins and/or their prodrugs, especially those belonging to the auristatins. The prodrugs are targeting to integrins and/or proteases, and activated by the aldolase antibody or the tumor-associated proteases. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3715.